Electrocatalyst Materials Structure
Professor Manish Chhowalla, from Rutgers University, leading researcher of this study, explained to Decoded Science how they made the material.
“We prepared a solution suspension of tungsten disulfide sheets with thickness of the order of nanometers; successively we deposited drops of this solution on the surface of solid support (glassy carbon or silicon). In some cases, we treated these sheets at 300 oC.
This treatment at high temperature remarkably affects the structure of the material; in fact, without this treatment WS2 has an octahedral geometry (1T structure) with metallic properties. After 300 oC treatment, on the other hand, the material has a trigonal prismatic structure (2H). The two structures are shown in the pictures below. ”
Effect on Hydrogen Evolution Reaction
The structure of the material has a remarkable effect on its properties and behavior in the hydrogen evolution reaction.
“We could see that the 1T form worked much better than the 2H” said Professor Chhowalla, “When all WS2 had the 2H structure, a greater amount of energy was necessary for the reaction to occur. For the 1T structure, on the contrary, the energy required was much smaller. Although it was higher than the energy required with platinum electrode, the difference was not very big.”
For mixed materials, containing both forms of WS2, Professor Chhowalla and his coworkers observed a positive linear correlation between the amount of 1T proportion in the material and the catalytic activity of the materials.
Creating Hydrogen: Important Results
According to Professor Chhowalla “these findings are important, as they show that inexpensive and earth abundant materials can be used to evolve hydrogen using minimal energy.
The structure of the material is the key factor in its efficiency. WS2 normally has a 2H geometry; in this case we made WS2 with a different structure, which worked better than the normal one. This is a point which has to be considered to improve WS2 efficiency even more and make it competitive with platinum.”
Reducing the expense involved in producing hydrogen could mean that more efficient and inexpensive hydrogen fuel-powered engines are on their way.
Voiry, D. et al. Enhanced catalytic activity in strained chemically exfoliated WS2 nanosheets for hydrogen evolution. (2013). Nature Materials, DOI: 10.1038/NMAT3700. Accessed July 11, 2013.
Usui, T. World budget of platinum. (2010). Accessed July 11, 2013.
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